Susan Fullerton-Shirey

NSF Graduate Research Fellow

Email: fullerton.3@nd.edu

Office address:
115 Fenske Laboratory
Pennsylvania State University
University Park, 16802

Undergraduate degree
BS Chemical Engineering, Penn State University (1998-2002)

Hobbies and interests:
Steelers, playing sports, piano, music, swimming

Duration: 2003-2009 (PhD)

Replacing the liquid with a solid polymer would eliminate toxicity as well as the need for a rigid casing because the polymer is solid. Without the casing, the battery would be lighter, and the polymer would allow the battery to be flexible likely leading to new and innovative portable devices. However, polymer-based electrolytes are not viable because room temperature conductivity is insufficient to power a portable device.

Conductivity quantifies how quickly lithium ions travel through the electrolyte from one electrode to the other. This speed is important because it controls how quickly electrons are produced to power the device. The low conductivity is not surprising since you would expect an ion to move more slowly through a solid polymer than through a liquid-phase electrolyte.

While several components of the battery present engineering challenges, the goal of my research is to understand how the lithium-ions move through the polymer electrolyte. We can use this information to modify the polymer so that the lithium-ions can move faster.

One well-known modification to improve conductivity is the addition of oxide nanoparticles. While the conductivity increases, it remains insufficient to power a portable device; furthermore, the mechanism by which the nanoparticles operate is not well-understood. Perhaps the nanoparticles attract lithium-ions to the surface, freeing them from strong coordination with the polymer host. Maybe the nanoparticles aggregate and create percolated networks, or channels, for the lithium-ions to speed along faster than they could through the bulk polymer. Or perhaps the nanoparticles increase the mobility of the polymer, thereby increasing the mobility of the lithium-ion.

The common theme among these hypotheses is that they involve understanding the structure and mobility of the electrolyte at the molecular level. An experimental technique that is well-suited for this type of investigation is neutron scattering. Specifically, I use small-angle neutron scattering to investigate structure (nanoparticle and/or lithium-ion aggregation, crystalline versus amorphous polymer domains, etc.) and quasi-elastic neutron scattering to investigate polymer dynamics (how fast the polymer moves in the presence of lithium-ions and nanoparticles). Details regarding neutron scattering can be found here.

Neutron scattering allows us to directly measure the spatial scale (angstroms to nanometers) and timescale (picoseconds to nanoseconds) relevant to this problem. In combination with ionic conductivity measurements, the neutron measurements reveal the structure and mobility at lithium concentrations and nanoparticle loadings that result in the maximum conductivity. This molecular-level information helps us to determine what further modifications could be made to boost conductivity to a practical value.

Publications:

1. Fullerton-Shirey SK, Maranas JK, "Effect of LiClO4 on the Structure and Mobility of PEO-Based Solid Polymer Electrolytes " Macromolecules 42, 2142 (2009)
   
2. S. K. Fullerton and J. K, Maranas "A Molecular Dynamics Study of the Structural Dependence of Boron Oxide Nanoparticles on Shape" Nano Letters 5, 363 (2005)
3. S.K. Fullerton and J. K. Maranas, "A Molecular Interpretation of Vitreous Boron Oxide Dynamics" J. Chem. Phys. 121, 8562 (2004)